Mix the cocoa powder, flour, and sugar in a mixing bowl. Slowly whisk in a bit of the milk to form a paste, then add the remaining milk to make a thin batter. Transfer to a large saucepan and, stirring constantly over medium heat, slowly bring to a boil. Remove from heat, add the grated chocolate and espresso, and stir to mix well. When the chocolate is completely melted, fill 6 (6-ounce) ramekins four-fifths full, and allow to cool.
Cover each with a dollop of whipped cream and sprinkle with the pine nuts. Serve immediately, or chill until needed.